title: An interpretation of the internal desynchronizations based on dynamics of the two-process model.
abstract: Daan's two-process model is known to be one of the most powerful models, covering various situations from free-running to sleep deprivation. In this study, bifurcation properties of the model dynamics are clarified using a circle map. In addition, the two-process model is applied to simulate the two distinct patterns (the period-prolonged: I and the period-shortened: II) of sleep-wake cycles during internal desynchronizations. We propose the novel interpretation that types I and II could be regarded as mutual entrainments between the body temperature rhythm and the sleep-wake cycle with the period ratios 3:4 and 3:2, respectively. From the bifurcation properties of the two-process model obtained above, the model is shown to be able to generate the respective type of mutual entrainment with an appropriate range of a parameter value, i.e, a gap between thresholds. The variable behavior of human circadian rhythm is suggested to be systematically understood based on the bifurcation properties of the two-process model.
authors.affiliation: Laboratory of Neurophysiology and Bioinformatics, Graduate School of Information Sciences, Tohoku University, Sendai, Japan. nakao@ecei.tohoku.ac.jp
authors.forename: M
authors.initials: M
authors.lastname: Nakao
authors.forename: H
authors.initials: H
authors.lastname: Sakai
authors.forename: M
authors.initials: M
authors.lastname: Yamamoto
mesh_terms: D000204:Activity Cycles; D001831:Body Temperature; D006801:Humans; D008954:Models, Biological; D012890:Sleep / Q000502:physiology; D014851:Wakefulness / Q000502:physiology